Embodiments of the present disclosure generally relate to multilevel converters and more specifically to a multilevel converter realized with a reduced number of fully controllable semiconductor switches.
As will be appreciated, a converter is employed to convert one form of power to another form. The introduction of three-level converters led to the advent of multilevel converters. Subsequently, several multilevel converter topologies were developed. The concept of a multilevel converter was established to achieve higher power via use of a series of semiconductor switches with several lower voltage direct current (DC) sources to perform power conversion by synthesizing a staircase voltage waveform. Capacitors, batteries, and renewable energy voltage sources can be used as the DC voltage sources. The multilevel converter offers several advantages over a conventional two-level converter that uses high switching frequency pulse width modulation (PWM). Furthermore, the multilevel converters are typically suitable for medium to high power applications. In recent times due to an increased number of high power applications, there is an increased demand for multilevel converters.
Conventionally, the multilevel converters typically include only fully controllable semiconductor switches. However, the use of the fully controllable semiconductor switches increases the cost of the converter because of the high cost of the fully controllable semiconductor switches. Another alternative converter is a diode rectifier which employs only diodes. Although, the diode rectifier is low in cost, the diode rectifier produces output waveforms with high distortion.